The present invention relates to an electrostatic voltage detecting device for detecting electrostatic voltage generated by electrostatic induction.
There is known a device for electrostatically recording and reproducing information signal such as picture image and sound. The electrostatic recording and reproducing device of this type has a recording medium including an insulating plate 2 formed of an insulative material such as Teflon (trade name) and capable of storing electric charge, and a conductive layer 4 formed on the insulating plate 2, as shown in FIG. 1. Information signal is recorded in the form of signal charge by applying a signal voltage to a metal needle electrode (not shown), which is moved relative to the insulating plate 2, so as to inject into the insulating plate 2 charges of an amount corresponding to the signal voltage applied. When it is required to read out information signal thus recorded, a reproducing electrode 6 is moved relative to the insulating plate 2 to generate a voltage between the reproducing electrode 6 and the signal charge. Electrostatic voltage thus sensed is applied, as a reproducing signal, to an output circuit 8 through a CR circuit which includes a resistor R1 and a capacitor C1, whereby a static distribution of electric charge stored in the insulating plate 2 can be detected. In the case of this electrostatic reproducing device, however, it is impossible to obtain a reproducing signal having a level accurately corresponding to the quantity of electrostatic charge injected into the insulating plate 2. In addition, this reproduced signal is low in its S/N ratio.